1. Field of the Invention
This invention relates to an apparatus for stretching a plastic raw material, particularly to an apparatus for stretching plastic dough having viscoelasticity, such as bread dough or confectionery dough. More particularly, it relates to such apparatus whereby stretching can be performed without a complex mechanism.
2. Description of the Prior Art
As one form of prior art apparatus to stretch dough such as bread dough or confectionery dough, a dough stretching apparatus as disclosed in U.S. Pat. No. 3,973,895 is frequently employed, in which apparatus conveyors are arranged in series and driven at progressively higher speeds, and a plurality of rollers, rotatable about their axes and along an endless roller path, are disposed above the conveyors.
However, in such a prior art apparatus, the movement of the rollers is achieved by a complex drive mechanism.
For example, a pair of chains is mounted to shafts of rollers, at both ends of rollers, to connect the rollers along an endless roller path. As the rollers are freely rotatably mounted to respective shafts, the rollers can rotate about their axes and progress along the endless roller path caused by the movement of the chains. Accordingly, the prior art apparatus requires a transmission mechanism to rotate rollers and a driving device to cause the chains to progress, thereby requiring a large space for these devices.